First operational experience with the LHC machine protection system when operating with beam energies beyond the 100MJ range

The Large Hadron Collider (LHC) at CERN has made remarkable progress during 2011, surpassing its ambitious goal for the year in terms of luminosity delivered to the LHC experiments. This achievement was made possible by a progressive increase of beam intensities by more than 5 orders of magnitude during the first months of operation, reaching stored beam energies beyond the 100MJ range at the end of the year, less than a factor of 4 from the nominal design value. The correct functioning of the machine protection systems is vital during the different operational phases, for initial operation and even more when approaching nominal beam parameters where already a small fraction of the stored energy is sufficient to damage accelerator equipment or experiments in case of uncontrolled beam loss. Safe operation of the machine in presence of such high intensity proton beams is guaranteed by the interplay of many different systems: beam dumping system, beam interlocks, beam instrumentation, equipment monitoring, collimators and absorbers. The strategy applied during 2011 to allow for an efficient but yet safe increase of the beam intensities is presented along with the associated risks and drawbacks of a too aggressive approach. The experience gained with the key systems of LHC machine protection since start-up of LHC luminosity operation will be discussed along with possibilities to further enhance machine availability whilst maintaining the current level of safety.